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Manu, S.
- Schumann Resonances Observed at Maitri, Antarctica:Diurnal Variation and its Interpretation in Terms of Global Thunderstorm Activity
Abstract Views :227 |
PDF Views:87
Authors
Affiliations
1 Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli 627 011, IN
2 Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai 410 218, IN
1 Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli 627 011, IN
2 Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai 410 218, IN
Source
Current Science, Vol 109, No 4 (2015), Pagination: 784-790Abstract
Schumann resonances (SRs) are the AC components of the global electric circuit and are excited by the lightning activity within the Earth-ionosphere waveguide. An induction magnetometer, which was operated from the Indian Antarctic station, Maitri (70.8°S, 11.7°E), served to examine the SR parameters, namely the amplitude and frequency, in the north-south (HNS) and east-west (HEW) magnetic components. The analysis for the first resonant mode presented in this work reveals a strong UT variation in its amplitude in seasonal as well as yearly timescales. The NS amplitude reveals a semi-diurnal variation with peaks at ~1000 and ~2100 UT, whereas the EW amplitude exhibits a strong diurnal variation with a pronounced peak at 1600 UT. The diurnal curves for the frequency for both components are similar in nature to those for the amplitude, but for a time shift. The diurnal trend in the amplitude is retained irrespective of seasons, whereas significant difference are noticed in the frequency behaviour between the summer and winter seasons, especially in the EW component. The observed diurnal variation in the SR intensity is explained in terms of the dominant thunderstorm activity centred over the three convectively active regions: Asia/Maritime Continent (Indonesia), South America and Africa. The diurnal variation in frequency depends not only on the location of the thunderstorm region with respect to the observer, but also on the ionospheric day/night conditions and the Earth-ionosphere cavity thickness.Keywords
Diurnal Variations, Global Electric Circuit, Lightning, Schumann Resonances.Full Text
- A Differential Electrometer for Vector Electric Field Measurements on a Balloon Platform
Abstract Views :286 |
PDF Views:91
Authors
Affiliations
1 Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli 627 011, IN
2 Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai 410 218, IN
1 Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli 627 011, IN
2 Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai 410 218, IN
Source
Current Science, Vol 111, No 4 (2016), Pagination: 624-626Abstract
Vector measurements of middle atmospheric electric fields are mostly carried out using a double-Langmuir probe technique on platforms like balloons and rockets. High impedances (up to 1013 ohms) and low signal levels (~few millivolts) are the factors that are to be considered in the design of an electrometer for one such experiment. Here, we offer a simple circuit concept that invokes an instrumentation amplifier capable of meeting our several needs, namely generating the guard voltage, ultra-high impedance (1015 ohms) input terminals, femtoampere bias current, differencing, gain setting, etc. all in one package. A three-channel differential electrometer was developed based on this concept and flown on a high-altitude balloon platform. Results reveal that the instrument is capable of detecting weak electric field variations at stratospheric altitudes.Full Text